1. Field of the Invention
The present invention relates to a playback apparatus and a playback method to play data recorded on a DVD (Digital Versatile Disk) or the like, and particularly to a playback apparatus and a playback method capable of carrying out special playbacks such as a high-speed and time search.
2. Description of Related Art
Program streams on a DVD video are managed on a VOBS (Video Object Set) basis, where the unit is for example a movie. The VOBS is made up of a plurality of VOBs (Video Object). The VOBS is a unit in which each data is recorded as one group on a disk. The VOB is made up of a plurality of cells, where the cell is for example one scene or clip in a movie. Moreover, the cell is made up of a plurality of VOBUs (Video Object Unit). The VOBU is 0.4 to 1.2 second unit and one or more GOP (Group of Picture) in MPEG2 format is included in a VOBU.
A VOBU has a navigation pack (N_PCK) having management information of the VOBU and the navigation pack is placed at the beginning of each VOBU. A navigation pack has VOBU_SRI (VOBU Search Information) and SP_SYNCA, and VOBU_SRI has a start address of a VOBU that is played before and after the playback time of VOBU including the VOBU_SRI for N seconds. Further, SP_SYNCA had address information of a subpicture that is synchronized with a video of VOBU having the SP_SYNCA to be played. To play a movie or the like, the navigation pack is previously read in so as to play according to the management information indicated by the navigation pack.
By the way, to carry out a time search (time specified playback) or high-speed search (forward/backward) on a DVD+RW having such data configuration, it is normally performed as follows. FIG. 12 is a view showing a data configuration of search information DSI. FIGS. 13 and 14 are views explaining a conventional high-speed searching method. FIG. 15 is a view explaining a high-speed searching method when VOBU_SRI crosses over cells. In this document, playbacks other than normal playbacks including a time search and high-speed search is referred to as a special search hereinafter.
As information defined in the DVD+RW standard used to perform these special playbacks (searching process), there is VOBU search information (VOBU_SRI) described in data search information (DSI) that is included in an navigation pack, as shown in FIG. 12. In the VOBU search information, search information up to BWDI_240 in the past direction and to FWDI_6 in the future direction exists. Accordingly assuming that playback time of one VOBU to be 0.5 second, VOBU start address up to 120 seconds before in the past direction and VOBU start address up to 3 seconds ahead in the future direction are described.
Forward/backward speed is determined by the number of skipping VOBU and the number of displaying sheet for one picture. Thus skipping many VOBUs or reducing display sheets increases the speed of searching. However the displaying sheets cannot be reduced extremely in relation to the appearance and decode processing time, thus the speed is practically determined by how much VOBUs are skipped to play.
However in the DVD+RW as shown in FIG. 13, for VOBU search information (VOBU_SRI), information up to only FWDI_6 (3 seconds ahead) exists in the future direction. Thus address cannot be skipped more than that in the future direction. Accordingly to carry out a high-speed search, the address is skipped to the farthest VOBU information (FWDI_6) in the future direction to obtain again search information from a disk corresponding to the VOBU and a high-speed search is accomplished by repeating the operation to skip to the farthest VOBU information (FWDI_6) in the future direction again according to the obtained data. Thus to realize the searching process only with the search information (DSI) defined in the DVD+RW standard, assuming that a unit playback time for one VOBU is 0.5 second and the number of frame making up one VOBU is 15 frames, the searching speed of a high-speed search can practically be increased up to 20×-speed for a forward.
Therefore, to accomplish 100×-speed as a normally common high-speed search, abovementioned 20×-speed may be repeated for 5 times as shown in FIG. 14. However there is a problem in this way that the process is complicated and takes more time.
Further, to carry out a time search only with the search information (DSI) defined in the DVD+RW the VOBU information (FWDI_6) in the farthest future direction in the search information is read out from the first VOBU of a title. Then the process to obtain again search information corresponding to the VOBU from a disk is overlapped. The method is to find a specified time by accumulating the time in this way. This method requires to search for future information before the high-speed search, thus it is not realistic to accomplish only with the data search information (DSI).
Furthermore, to accomplish searching process such as a high-speed search and time search only with the search information (DSI) defined in the DVD+RW standard, as shown in FIG. 15, the search information is cut off in the boundary between cells making up a title. Thus to carry out a search crossing over cells, a recalculation is needed, thereby complicating the computation process.
As discussed above, to accomplish a searching process such as a time search and high-speed search only with the search information (DSI) defined in the DVD+RW standard, there is no other method to find a specified time but to overlap the process to obtain again search information from a disk so as to accumulate time. There is another problem that this causes to complicate the process.
To overcome these problems, a method is disclosed in Japanese Unexamined Patent Application Publication No. 2005-521189 that a high-speed search is carried out using video title set video object unit address map VTS_VOBU_ADMAP. FIGS. 16 to 18 are views explaining the method of high-speed search disclosed in Japanese Unexamined Patent Application Publication No. 2005-521189. FIG. 5 is a view explaining VTS_VOBU_ADMAP.
In the technique disclosed in Japanese Unexamined Patent Application Publication No. 2005-521189, a special playback is carried out by calculating playback of each VOBU that does not exist in the standard. Specifically as shown in FIG. 16, a start address (C_FVOBU_SA) of a first VOBU and a start address (C_LVOBU_SA) of a last VOBU of a playback cell (C_PBI#m) in a playback information table (C_PBIT) that is included in program chain information (PGCI) are obtained in relation to a cell currently being played. Then VTS_VOBU_ADMAP shown in FIG. 5 is referred from the start/last VOBU address information of the cell to calculate the number of VOBU in the cell. Moreover, cell playback time (C_PBTM) in the cell playback information table (C_PBIT) is obtained and divided by the number of VOB calculated as in the foregoing so as to obtain the playback time for one VOBUS in a cell currently being played.
Specifically as shown in FIG. 17, VOBU number m is read out from the address of the start address C_FVOBU_SA of the first VOBU of a cell and VOBU number n is read out from the start address C_LVOBU_SA of the last VOBU of a cell in order to calculate the number or VOBUs (n-m) in the cell. Then playback time t3 for one VOBU is calculated by cell playback time C_PBTM/(n-m).
After that as shown in FIG. 18, a high-speed search is carried out using the playback time t3. For example a case is described hereinafter in detail where the unit average time t3 for one VOBU is 0.5 second and the number of frame in one VOBU is 15. One second is made up of 30 frames. With an instruction for a 5× high-speed search, when 6 frames are displayed for one playback, to accomplish 5× speed, it needs to be played once in 2 VOBUs (30 frames). That is, 5×-speed playback is carried out by playing 30 frames by 6 frames. In such case, assuming that VOBU number currently being played to be #n, VOBU is accessed in the order of: #n+2, #n+4, #n+6 . . . and played by 6 frames each. Accordingly the playback controller 30 obtains addresses #n+2, #n+4, #n+6 by referring to VTS_VOBU_ADMAP to carry out a high-speed search.
Likewise, to accomplish 10×-speed by displaying 6 frames for one playback, it needs to be played once in 4 VOBUs (which is 60 frames). Further to accomplish 30× speed by playing 4 frames in one playback, it needs to be played by 8 VOBUs (which is 120 frames). Likewise, to accomplish 50× and 100× speeds by playing 4 frames, it needs to be played by 13 VOBUs (which is 195 frames) and 27 VOBUs (which is 405 frames) respectively.
Here in Japanese Unexamined Patent Application Publication No. 2005-521189, to obtain playback time for one VOBU, it is performed for a cell currently being played. This means that to obtain playback time for one VOBU, PGCI for full title is referred when playing full title and PGCI for play list title is referred when playing play list title.
However it has now been discovered that there is a following problem occurred in the technique disclosed in Japanese Unexamined Patent Application Publication No. 2005-521189 because the technique assumes that PCGI has always correct information in relation to a searching for a play list title. That is, for a play list title, it is not a problem even if correct PGCI is not recorded as a standard. If PCGI is different from an actual title, information (PL match) indicating the difference is added. FIG. 19 is a view explaining a PL match. A PL match is described in a PL match in a record mode (REC_MODE) of VRMI recording information (VRMI_RECI) of video recording management information (VRMI). If PGCI of play list title is invalid, the information indicating the invalid PGCI is written in the PL match.
There is a problem in the technique disclosed in Japanese Unexamined Patent Application Publication No. 2005-521189 that when playing a play list title with incorrect PL match, search process cannot be carried out. Especially for the DVD+VR standard, the abovementioned problem becomes pronounced as the play list title is used more than full title.